This invention relates to a gas-insulated electric apparatus wherein an improved compound is applied to the junction of flanges set adjacent to each other to connect a plurality of metal pressure vessels used, for example, with a gas-insulated electric apparatus.
As shown in FIG. 1, each case 2 of a gas-insulated electric apparatus which has a ground potential contains a conductor 1 and high voltage insulation gas 3 (for example, SF.sub.6 gas) with an insulator (not shown) interposed therebetween. All adjacent cases 2 are joined together by flange sections 4 which are formed at the mutually facing ends of the cases 2 and electrically and mechanically connected together by means of seal packing 5, bolts 6b and nuts 6a.
Where the case 2 is grounded at many points as shown in FIG. 1, namely where support legs 7 electrically and mechanically connected to the case 2 are joined to a grounding net 9 at several points by means of a grounding line 8, then induced currents i, i' flow through a closed loop formed of the case 2-support legs 7-grounding lines 8-grounding net 9. As seen from FIG. 2, the induced currents i, i' also run through the flange junction 10. This flange junction constitutes an important section sealed with gas. Water tends to seep into that portion of the flange junction surface 10 which is exposed to the open air, with the possibility that the portion of the flange junction surface 10 to which the packing 5 is attached is rotten, probably causing the sealed gas to leak out. Therefore, it is necessary to apply a waterproof and rust preventing agent to the flange junction surface 10 to avoid the seeping of water thereinto. Since, the aforementioned induced currents i, i' run through the flange junction 10, the process is proposed which applies, for example, a conductive compound to said flange junction 10 to draw out said induction currents therefrom.
However, the conventional waterproof and rust-preventing agents have merits and demerits as indicated in Table 1 below.
TABLE 1 ______________________________________ Properties of Conventional Water- proof and Rust-Preventing Agents Kind of waterproof Waterproof and and rust-preventing rust-preventing Influence Conductive agents property on packing capacity ______________________________________ Alcan Universal Joint Compound* medium great large (mineral oil + TiO.sub.2) Solidifying silicone rubber great none none Non-solidifying liquid gasket** great small none Silicone grease TSK 5401L*** great none small ______________________________________ *Trade mark, from Alcan Asia Ltd. **Vegetable oil + Talc + phenol etc. ***Trade mark, from Toshiba Silicone Co. Ltd.
Therefore, the conventional process of resolving the above-mentioned difficulties comprised applying waterproof and rust-preventing solidifying silicone rubber, nonsolidifying liquid gasket or silicone grease, and electrically short circuiting all adjacent cases 2 by shunt 11 to let the aforesaid induced currents i, i' bypass the flange junction.
However, the construction of a shunt over the whole assembly of the flange junction and associated parts is extremely expensive and involves a complicated arrangement.